Amantadine is a well known anti-viral agent which has been commercially available for years under the brand name Symmetrel. Its primary use is for preventing influenza A infections though higher doses (25-50 .mu.g/ml) can inhibit other viruses as well (Hayden et al, Principles and Practice of Infectious Diseases, 2nd ed. Wiley, N.Y. (1985) p. 270-286). Its mode of action is thought to be at an early stage in replication probably at the state of uncoating. Attachment and penetration of the virus to a cell is not affected by amantadine (Skehel et al, J. Gen. Virol. 38 p. 97-110 (1978).